When New York Herald reporter Henry Morton Stanley found him in a small African village on November 10, 1871, reclusive British explorer David Livingstone had lost contact with the outside world for six years. His journal account of the mass slaughter of the village Nyangwe, brought back by Stanley, horrified the public and led to the end of the African slave trade. But Livingstone may not have told the entire story of the massacre. To discover the truth, PBS's Secrets of the Dead follows a team of experts who use state-of-the-art imaging technology to decipher Livingstone's newly discovered, faded field diary in an effort to determine what really happened in Nyangwe. Why was the private diary scrawled on newspaper in berry juice and not on writing paper in ink? How did Livingstone's obsession with discovering the source of the Nile cause him to stray from his principles? How did the death of his wife affect him? For the first time in 140 years, the secrets Livingstone tried to keep hidden are revealed.